**Table of Contents**Show

## Understanding Mole Concept

The mole is a fundamental unit in chemistry used to express amounts of chemical substances. It represents a specific number of entities, such as atoms, molecules, or ions. One mole of any substance contains **Avogadro’s number** of entities, which is approximately 6.022 x 10^23.

## The Formula for Calculating Number of Molecules

When calculating the number of molecules in a given number of moles of a substance, you can use the following formula:

**Number of molecules = Number of moles x Avogadro’s number**

## Calculating Number of Molecules in 2.5 Moles of NaCl

**NaCl** is a compound made up of sodium ions (Na+) and chloride ions (Cl-). The formula weight of NaCl is approximately 58.5 g/mol. To determine the number of molecules in 2.5 moles of NaCl, we can use the formula mentioned above.

## Step-by-Step Calculation

- Calculate the molar mass of NaCl: Na (22.99 g/mol) + Cl (35.45 g/mol) = 58.44 g/mol
- Now, multiply the molar mass by the number of moles: 58.44 g/mol x 2.5 mol = 146.1 g
- Convert the mass to molecules using Avogadro’s number: 146.1 g x (1 mol / 58.44 g) x (6.022 x 10^23 molecules / 1 mol)

## Final Calculation

After performing the calculations, we find that there are approximately **3.6 x 10^24 molecules** in 2.5 moles of NaCl.

## Conclusion

Understanding the concept of moles and Avogadro’s number allows us to calculate the number of molecules in a given amount of substance accurately. In the case of 2.5 moles of NaCl, there are approximately 3.6 x 10^24 molecules present.